Mitigating crosstalk in tissue conduction audio systems

ABSTRACT

An audio system on a headset presents audio content via tissue conduction to an inner ear of a first ear of a user. The system monitors, via one or more sensors on the headset, data about the presented audio content. The one or more sensors including at least one sensor configured to capture data about the presented audio content at a second ear of the user. The system estimates array transfer functions (ATFs) associated with the data, and generates sound filters for the transducer array using the estimated ATFs. The system presents adjusted audio content based in part on the sound filters. The adjusted audio content has a damped region at the second ear such that the amplitude of the adjusted audio content at the first ear has a higher amplitude than at the second ear.

BACKGROUND

The present disclosure generally relates to tissue conduction audiosystems, and specifically relates to the mitigation of crosstalk intissue conduction audio systems.

Head mounted displays (HMDs) may be used to present virtual and/oraugmented information to a user. For example, an augmented reality (AR)headset or a virtual reality (VR) headset can be used to simulate anaugmented/virtual reality. Conventionally, a user of the AR/VR headsetwears headphones to receive, or otherwise experience, computer generatedsounds, video, and haptic. However, wearing headphones suppresses soundfrom the real-world environment, which may expose the user to unexpecteddanger and also unintentionally isolate the user from the environment.Moreover, headphones separated from the outer casing or a strap of theHMD may be aesthetically unappealing and may be damaged through use.

SUMMARY

A method for mitigating crosstalk in a tissue conduction audio system.The method presents, via a transducer array of a headset, audio contentvia tissue conduction (e.g., bone conduction and/or cartilageconduction) to a first ear of a user. A sensor array of the headsetmonitors data, at both the first and second ears of the user, about thepresented audio content. Array transfer functions (ATFs) associated withthe audio content are estimated based on the sensor data. Sound filtersare generated using the estimated ATFs. The sound filters are applied totransducer signals from the transducer array, which present adjustedaudio content to the user's ears. The amplitude of the adjusted audiocontent at the first ear is higher than the amplitude of the adjustedaudio content at a damped region at the second ear. In some embodiments,the amplitude of the adjusted audio content at the second ear is higherthan the amplitude of the adjusted audio content at a damped region atthe first ear. In some embodiments, a transitory computer readablemedium is configured to store program code instructions. The codeinstructions, when executed by a processor, cause the processor toperform steps of the method.

In some embodiments, an audio system is part of a headset (e.g., neareye display, head mounted display). The audio system includes atransducer array, one or more sensors, and a controller. The transducerarray is configured to present audio content via tissue conduction to aninner ear of a first ear of a user. The one or more sensors on theheadset are configured to monitor data about the presented audiocontent, the one or more sensors including at least one sensorconfigured to capture data about the presented audio content at a secondear. The controller is configured to estimate array transfer functions(ATFs) associated with the data, and generate sound filters for thetransducer array using the estimated ATFs. The controller instructs thetransducer array to present adjusted audio content, based in part on thesound filters, wherein the adjusted audio content has a damped region atthe second ear such that the amplitude of the audio content at the firstear has a higher amplitude than at the second ear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a headset, in accordance with one or moreembodiments.

FIG. 2 is a side view of a portion of a headset, in accordance with oneor more embodiments.

FIG. 3A illustrates a sound field prior to crosstalk mitigation, inaccordance with one or more embodiments.

FIG. 3B illustrates a sound field after crosstalk mitigation, inaccordance with one or more embodiments.

FIG. 4 is a block diagram of an example audio system, in accordance withone or more embodiments.

FIG. 5 is a process for mitigating crosstalk in a tissue conductionaudio system, in accordance with one or more embodiments.

FIG. 6 is a block diagram of an example artificial reality system, inaccordance with one or more embodiments.

The figures depict various embodiments for purposes of illustrationonly. One skilled in the art will readily recognize from the followingdiscussion that alternative embodiments of the structures and methodsillustrated herein may be employed without departing from the principlesdescribed herein.

DETAILED DESCRIPTION

A tissue conduction audio system presents audio content to a user usingone or both of bone conduction and cartilage conduction. Tissueconduction delivers audio content to the user using cartilage conductionand/or bone conduction. Tissue conduction may occur via bone conductionand/or cartilage conduction, that vibrates bone and/or cartilage togenerate acoustic pressure waves.

A bone conduction audio system uses bone conduction for providing audiocontent to the ear of a user while keeping the ear canal of the userunobstructed. The bone conduction audio system includes a transducerassembly that generates tissue born acoustic pressure wavescorresponding to the audio content by vibrating tissue in a user's headthat includes bone, such as the mastoid. Tissue may include e.g., bone,cartilage, muscle, skin, etc. For bone conduction, the primary pathwayfor the generated acoustic pressure waves is through the bone of thehead (bypassing the eardrum) directly to the cochlea. In boneconduction, the acoustic pressure waves may just travel through bone toreach the cochlea, bypassing air conduction pathways. The cochlea turnstissue borne acoustic pressure waves into signals which the brainperceives as sound.

A cartilage conduction audio system uses cartilage conduction forproviding audio content to an ear of a user. The cartilage conductionaudio system includes a transducer assembly that is coupled to one ormore portions of the auricular cartilage around the outer ear (e.g., thepinna, the tragus, some other portion of the auricular cartilage, orsome combination thereof). The transducer assembly generates airborneacoustic pressure waves corresponding to the audio content by vibratingthe one or more portions of the auricular cartilage. This airborneacoustic pressure wave may propagate toward an entrance of the ear canalwhere it would be detected by the ear drum. However, the cartilageconduction audio system is a multipath system that generates acousticpressure waves in different ways. For example, vibrating the one or moreportions of auricular cartilage may generate: airborne acoustic pressurewaves that travel through the ear canal; tissue born acoustic pressurewaves that cause some portions of the ear canal to vibrate therebygenerating an airborne acoustic pressure wave within the ear canal; orsome combination thereof.

Note that the tissue conduction system is different from airborne audiosystems (e.g., a conventional speaker) for at least the reason that thetissue conduction system can generate airborne acoustic waves byvibrating tissue (bone, cartilage, etc.) of the user. The vibration ofthe tissue creates several acoustic pathways, such that the acousticpressure waves may travel through tissue, bone, air, or a combinationthereof. In contrast, a typical airborne audio system uses speakers withvibrating membranes that directly displace air to generate airborneacoustic waves.

The audio system may be part of a headset (e.g., near eye display or ahead mounted display). The audio system includes a transducer array,sensors, and a controller. The transducer array presents audio contentvia tissue conduction to a headset user's inner ear. The sensors capturedata about the initially presented audio content at both ears of theheadset user. The controller estimates array transfer functions (ATFs)associated with the audio content presented at each ear, and generatessound filters using the estimated ATFs. ATFs comprise a collection oftransfer functions that characterize how audio content produced by thetransducer array is received by the sensor array. A transfer functiondefines a relationship between sound produced at its source location,i.e., a transducer, and where it is detected, i.e., a sensor. Parametersthat help define the relationship may include frequency, amplitude,time, phase, duration, and a direction of arrival (DoA) estimation,among others. In some embodiments, Eigen value decomposition is used todetermine a transfer function. In other embodiments, singular-valuedecomposition is used to determine the transfer function. The transducerarray presents audio content to both ears, adjusted in part by thegenerated sound filters, such that crosstalk caused by tissue conductionis mitigated. The controller designates a first ear as a “bright zone,”and a second ear as a damped, “quiet zone.” The adjusted audio contenthas a lower amplitude at the quiet zone than at the bright zone, and insome cases, there may be a null in the sound field at the quiet zone,where no audio content is perceivable.

Presenting audio content via tissue conduction transducers may result incrosstalk due to, e.g., sharing of the user's cranial bone as a commonmedium for transmitting the vibrations. By dampening sound at regionsthat crosstalk may be perceived, the audio system described hereinmitigates at least some of the crosstalk that results from tissueconduction.

Embodiments of the invention may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,and any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to, e.g., createcontent in an artificial reality and/or are otherwise used in (e.g.,perform activities in) an artificial reality. The artificial realitysystem that provides the artificial reality content may be implementedon various platforms, including a head-mounted display (HMD) connectedto a host computer system, a standalone HMD, a mobile device orcomputing system, or any other hardware platform capable of providingartificial reality content to one or more viewers.

System Overview

FIG. 1 is a diagram of a headset 100, in accordance with one or moreembodiments. The headset 100 presents media to a user. The headset 100includes an audio system and a frame 110. In general, the headset may beworn on the face of a user such that content is presented using theheadset. Content may include audio and visual media content that ispresented via the audio system and a display, respectively. In someembodiments, the headset may only present audio content via the headsetto the user. The frame 110 enables the headset 100 to be worn on theuser's face and houses the components of the audio system. In oneembodiment, the headset 100 may be a head mounted display (HMD).

The audio system presents audio content to the user of the headset. Theaudio system is a tissue conduction system. The audio system includes,among other components, a transducer array, a sensor array, and acontroller 170. The audio system may provide audio content via tissueconduction, also generating some level of crosstalk as a byproduct ofits operation. For example, sound emitted to a first inner ear of theuser may also be received by the user's other inner ear, due tovibrations to tissue near the first ear transmitting through the user'scranial bone to the user's other inner ear. In some embodiments, theacoustic waves may be transmitted through tissue other than the cranialbone. Additional details regarding the audio system are discussed belowwith regard to FIGS. 2-6.

The transducer array generates audio content (i.e., acoustic pressurewaves) in accordance with vibration instructions from the controller170. In some embodiments, the audio content may include a referenceaudio signal. For example, the reference audio signal may be contentfrom the user, such as music, a speech, or other user preferred content.In other embodiments, the reference audio signal may cover a largefrequency range, such as a maximum length sequence, a pseudo random pinknoise, a pseudo random white noise, a linear sinusoidal sweep, alogarithmic sinusoidal sweep, or some combination thereof. Thetransducer array also presents filtered audio content to the user, afterthe audio content has been adjusted as per the controller'sinstructions. The transducer array is further described with respect toFIGS. 3A-B.

The transducer array directly vibrates tissue (e.g., bone, skin,cartilage, etc.) to generate an acoustic pressure wave. The transducerassembly may include one or more transducers. A transducer (alsoreferred to as a tissue conduction transducer) may be configured tofunction as a bone conduction transducer or a cartilage conductiontransducer. In some embodiments, each transducer array may include oneor more transducers to cover different parts of a frequency range. Forexample, a piezoelectric transducer may be used to cover a first part ofa frequency range and a moving coil transducer may be used to cover asecond part of a frequency range. In some embodiments, the transducerarray may include transducers that serve as medical implants, such ascochlear implants.

The bone conduction transducers generate acoustic pressure waves byvibrating bone/tissue in the user's head. A bone conduction transduceris coupled to an end piece of the frame 110 and may be configured to bebehind the auricle coupled to a portion of the user's skull. The boneconduction transducer receives vibration instructions from thecontroller 170, and vibrates a portion of the user's skull based on thereceived instructions. The vibrations from the bone conductiontransducer generate a tissue-borne acoustic pressure wave thatpropagates toward the user's cochlea, bypassing the eardrum.

The cartilage conduction transducers generate acoustic pressure waves byvibrating one or more portions of the auricular cartilage of the ears ofthe user. A cartilage conduction transducer is coupled to a temple armof the frame 110 and may be configured to be coupled to one or moreportions of the auricular cartilage of the ear. For example, thecartilage conduction transducer may couple to the back of an auricle ofthe ear of the user. The cartilage conduction transducer may be locatedanywhere along the auricular cartilage around the outer ear (e.g., thepinna, the tragus, some other portion of the auricular cartilage, orsome combination thereof). Vibrating the one or more portions ofauricular cartilage may generate: airborne acoustic pressure wavesoutside the ear canal; tissue born acoustic pressure waves that causesome portions of the ear canal to vibrate thereby generating an airborneacoustic pressure wave within the ear canal; or some combinationthereof. The generated airborne acoustic pressure waves propagate downthe ear canal toward the ear drum.

The sensor array monitors the audio content emitted by the transducerarray. The sensor array includes a plurality of sensors. In theillustrated embodiments, the sensor array includes a sensor 140A and asensor 140B. The sensors 140A, 140B may be, for example, a microphone,an accelerometer, other acoustic sensor, or some combination thereof.The sensor array monitors audio content provided by the transducer arrayusing data from the sensors 140A, 140B. The sensor array generatessensor data based on the monitored audio content. Note that themonitored audio content may have propagated through a head of the userprior to being captured by a sensor. For example, audio content providedby the transducer 120A may be detected at the sensor 140B.

In some embodiments, the transducers 120A-D and sensors 140A-B may bepositioned in different locations within and/or on the frame 110 thanpresented in FIG. 1. For example, in some embodiments, the sensors140A-B may be microphones configured to fit within an ear of the user.The headset may include transducers and/or sensors varying in numberand/or type than what is shown in FIG. 1.

The controller 170 controls the tissue conduction system. The controller170 may receive audio data (e.g., music) from local memory or someexternal entity (e.g., a console, remote server, etc.) for presentationto the user. The controller 170 generates vibration instructions basedon the received audio data, and provides the vibration instructions tothe transducer array. In some embodiments, the vibration instructionsare such that the transducer array generates a reference audio signal.

The controller 170 generates ATFs using sensor data from the sensorarray. The ATFs, as described above, comprise a number of transferfunctions (e.g., a transfer function for each sensor) that characterizethe way audio content (e.g., the audio reference signal) is received bythe sensor array. The controller 170 uses the ATFs to generate soundfilters. The sound filters that are applied to the audio data to adjustthe audio content presented by the transducer array. As described ingreater detail below with regard to FIG. 3A-6 the adjusted audio contentmitigates crosstalk in the audio content presented by the transducerarray. Operation of the controller 170 is described in detail below,with regard to FIGS. 3A, 3B. and 4.

FIG. 2 is a side view 200 of a portion of a headset 205, in accordancewith one or more embodiments. The headset 205 is an embodiment of theheadset 100. The headset 205 presents audio content to the user, by atissue conducting audio system. The headset 205 rests in part on theuser's ears, such that it may be in proximity to a pinna 210 of an earof the user. The headset 205 includes, among other components, atransducer array and a sensor array. The transducer array includes agroup of transducers 230A, 230B, and the sensor array comprises a groupof sensors including a sensor 245. The transducers 230A, 230B areembodiments of transducers 120A, 120C, and sensor 245 is an embodimentof sensor 140A.

The transducers 230A, 230B provide audio content for one or both ears ofthe user. The transducers 230A, 230B are proximate to and/or coupled tovarious tissue on or near the ear of the user. Coupling may be such thatthere is indirect and/or direct contact between some or all of thetransducers 230A, 230B and the tissue of the user. For example, thetransducer 230A may be a cartilage conduction transducer that couples toa back of the pinna or top of the pinna 210 of an ear of the user. Thetransducer 230B may be a bone conduction transducer that couples to aportion of a bone near the ear. The transducers 230A, 230B vibrate thetissue they are coupled to, generating a range of acoustic pressurewaves, detected as sound by a cochlea of the user's inner ear (not shownin FIG. 2).

In some embodiments, the headset 205 may include a combination of one ormore bone conduction and cartilage conduction transducers. In someembodiments, the headset 205 may include one or more air conductiontransducers (not shown) and provide audio content to the user by acombination of air conduction and tissue conduction.

The sensor 245 monitors the audio content presented by the transducerarray. The sensor 245 is an embodiment of sensor 140A. The sensor 245 ispositioned on the headset to detect the acoustic pressure waves producedby the conduction transducers 230A-B and/or other tissue conductiontransducers (e.g., those located near the user's other ear). In someembodiments, the sensor 245 may be positioned within the ear canal. Thesensor 245 may be part of a sensor array positioned on or near theheadset, wherein the sensor array includes a plurality of sensors. Thesensor array may include a plurality of acoustic sensors similar tosensor 245, in addition to sensors designated for use other thanmeasuring audio data. Other sensors the sensor array may includeinertial measurement units (IMUs), gyroscopes, position sensors,accelerometer, or a combination thereof. At the other ear of the user,the audio system includes another group of transducers and at leastanother sensor, included in the headset's transducer array and sensorarray, respectively.

Crosstalk Mitigation

FIG. 3A illustrates a sound field 300 prior to crosstalk mitigation, inaccordance with one or more embodiments. An audio system provides audiocontent to a user of the headset by generating the sound field 300. Theaudio system may be part of a headset (e.g., the headset 100). The soundfield 300 includes at least sound source regions 310 and 320, transducergroups 350A and 350B, and sensor groups 360A and 360B. The transducergroups 350A and 350B are part of a transducer array, while the sensorgroups are part of a sensor array, as described in further detail withrespect to FIG. 4.

The sound field 300 is a region in which audio content from one or bothof the transducer groups 350A, 350B propagates. Note that while thesound field 300 is shown as having a rectangular geometry forsimplicity. In actuality, it would correspond to a head of the user. Thesound source regions 310 and 320 are regions within the sound field 310that would include, e.g., an inner ear, an ear drum, an ear canal of theuser, or some combination thereof. For example, the sound source region310 may correspond to an inner ear for a right ear of a user, and thesound source region 320 may correspond to an inner ear for a left ear ofthe user.

The transducer groups 350A, 350B generate the sound field 300 andthereby provide audio content to the sound source regions 310 and 320,respectively. The transducer groups 350A, 350B may comprise a number oftransducers, such as transducers 230A, 230B shown in FIG. 2. Thetransducer array includes a collection of the transducer groups 350A,350B. In the illustrated embodiment, the sound field 300 is meant to bepresented to the sound source region 310, but not the sound sourceregion 320. Note that because the sound field 300 is within a head ofthe user, presenting audio content via tissue conduction transducers mayresult in crosstalk due to, e.g., sharing of the user's cranial bone asa common medium for transmitting the vibrations. Accordingly, it can bedifficult to selectively target audio content to a single sound sourceregion (e.g., to sound source region 310, but not to the sound sourceregion 320, or vice versa). As shown in FIG. 3A, for example, if thetransducer group 350A produced audio content in a sound field 300 at thesound source region 310, the sound field 300 reaches the sound sourceregion 320 as well, thereby resulting in crosstalk. And for simplicitythe crosstalk is shown as the sound field 300 overlapping with the soundsource region 320.

The sensor array monitors audio content in the sound field 300. Thesensor array monitors audio content produced by the transducer group350A and/or the transducer group 350B via the sensor groups 360A, 360B.The sensor groups 360A, 360B coincide with the sound source region 310and 320, respectively, such that each sound source region is monitoredby a designated sensor group. The sensor groups 360A, 360B each compriseone or more sensors, such as sensor 245 as shown in FIG. 2. The sensorgroups 360A is configured to monitor audio content at the sound sourceregion 310 and the sensor group 360B is configured to monitor audiocontent at the sound source region 320.

In some embodiments, a transducer group is positioned on and/or near afirst ear of the user, with another transducer group positioned onand/or near the second ear of the user. Similarly, a sensor group ispositioned in proximity to the first ear, with another sensor grouppositioned in proximity to the second ear.

A controller (not shown) of the audio system processes the sound datacaptured by the sensor groups 360A, 360B, to generate sound filters. Thesound filters are used to present adjusted audio content, via thetransducer array that acts to mitigate crosstalk. This is furtherdescribed with respect to FIGS. 3B and 4 below.

FIG. 3B illustrates a sound field 315 after crosstalk mitigation, inaccordance with one or more embodiments. The sound field 315 isgenerated by the audio system. The sound field 315 is substantiallysimilar to the sound field 300 described in FIG. 3A, but modified toinclude a damped region 370. The damped region 370 helps mitigate atleast some of the crosstalk produced by the transducers in thetransducer groups 350A, 350B.

The transducer group 350A and/or the transducer group 350B produceadjusted audio content around in accordance with instructions from thecontroller (not shown). In the illustrated embodiment, the adjustedaudio content is such that a damped region 370 is formed in the soundfield 315. As described with respect to FIG. 3A, the sound field 300 mayreach the sound source region 320 due to crosstalk. By damping the soundperceived at the sound source region 320, i.e., an inner ear, the audiosystem can mitigate sound being perceived at the sound source region320, thereby reducing crosstalk.

In the illustrated embodiment, the sound source region 320 is designateda “quiet zone.” A quiet zone is a sound source region that is enclosedby a damped region. A damped region is a location in a sound field wherethe audio content is substantially reduced relative to portions of thesound field bordering the damped region. The damped region may bedefined as having an acoustic amplitude below a threshold level fromsound outside the damped region that is part of the sound field. In someembodiments, the gradient between the sound field bordering the dampedregion and the threshold level may drop off exponentially. The gradientmay be tied to the wavelength or wavenumber of the specific sound field.The size of the damped regions may be determined based on the wavelengthof the received sound, which is encoded in the ATF and used for thesound filters.

In some embodiments, the damped region may be a null. A null is alocation in a sound field where an amplitude is essentially zero.Accordingly, as the sound source region 320 is within the damped region320, the audio content perceived at the sound source region 320 issubstantially reduced, and in some cases it is low enough such that itwould not be perceivable by the left ear of the user.

In the illustrated embodiment, the sound source region 310 is designateda “bright zone.” A bright zone is a sound source region of the soundfield that is not within a damped region. Note in some embodiments, thebright zone also may include some amplification of the sound field. Forexample, the bright zone may be such that an amplitude of audio contentis increased relative to portions of the sound field bordering thebright zone.

The controller estimates one or more ATFs that characterize therelationship between the sound played by the transducer array and thesound received by the sensor array using the data captured by the sensorarray. The controller generates sound filters based on the estimated oneor more ATFs. The sound filters adjust the audio output produced by thetransducer array. For example, at the damped region 370, the soundfilters may result in audio content with attenuated amplitudes. Theprocess of estimating ATFs and generating sound filters is described infurther detail with respect to FIG. 4. The controller instructs thetransducer groups 350A, 350B to present filtered and thereby adjustedaudio content at the sound source regions 310, 320.

At the quiet zone, the transducer group 350B presents filtered audiocontent to the sound source region 320. The user's inner ear near thedamped region 370, i.e., sound source region 320, perceives sound with alower amplitude than the sound produced at the bright zone, near thesound source region 310. Damping the audio content at the sound sourceregion 320, where crosstalk was perceived in FIG. 3A, results in themitigation of at least some of the crosstalk heard by the user. In someembodiments, some portion of the audio content may be produced at thesound source 320, for the inner ear at the sound source region 320 toperceive. The amount of dampening at the damped region 370 may accountfor the audio content to be produced at the sound source 320. Forexample, crosstalk perceived at that inner ear may be damped such thatthe audio content meant for the inner ear is perceivable.

FIG. 4 is a block diagram of an example audio system 400, according toone or more embodiments. The audio system 400 may be a component of aheadset (e.g., headset 100) that provides audio content to the user. Theaudio system 400 includes a transducer array 410, a sensor array 420,and a controller 430. The audio systems described in FIGS. 1-3B areembodiments of the audio system 400. Some embodiments of the audiosystem 400 include other components than those described herein.Similarly, the functions of the components may be distributeddifferently than described here. For example, in one embodiment, thecontroller 430 may be external to the headset, rather than embeddedwithin the headset.

The transducer array 410 provides audio content to the user. Thetransducer array 410 may comprise a number of transducer groups (e.g.,the transducer groups 350A, 350B). Each transducer group includes one ormore transducers (e.g., transducers 120A, 120B, 120C, and 120D) that maybe used to provide the audio content to the user. The transducers may betissue conduction transducers, such as bone conduction transducers,cartilage conduction transducers, or some combination thereof. Note insome embodiments, the transducers may also include one or more airtransducers (i.e., speakers). The transducer array 410 provides audiocontent to the user over a total range of frequencies. For example, thetotal range of frequencies is 20 Hz to 20 kHz, generally around theaverage range of human hearing. The transducers in the transducer array410 are configured to vibrate over various ranges of frequencies. In oneembodiment, each transducer in the transducer array 410 operates overthe total range of frequencies. In another embodiment, one or moretransducers operate over a low subrange (e.g., 20 Hz to 500 Hz), while asecond set of transducers operates over a high subrange (e.g., 500 Hz to20 kHz). In some embodiments, the various ranges of frequencies maypartially overlap with.

The tissue conduction transducers in the transducer array 410 generateacoustic pressure waves in accordance with instructions received by thecontroller 430. The transducers are coupled to tissue near the user'sear, such as cartilage or bone, and vibrate the tissue to produce thesound waves. The acoustic pressure waves are detected by the ear drumand/or inner ear of the user, such as at the cochlea. In anotherembodiment, the transducers are coupled to the user's jaw or skull,rather than tissue near the ear. In some embodiments, the transducerarray 410 may include air conduction transducers that vibrate togenerate airborne acoustic pressure waves perceivable by the cochlea ofthe user's ear.

The sensor array 420 detects sound produced by the transducer array 410.The sensor array 420 may include one or more sensor groups (e.g., thesensor groups 360A, 360B). A sensor group includes one or more sensors(e.g., sensor 245). A sensor may be, e.g., a microphone, a vibrationsensor, an accelerometer, or any combination thereof. In someembodiments, a sensor may be a component of a hearing aid or cochlearimplant. The sensor array 420 is configured to monitor the audio contentgenerated by the transducer array 410 using sensors in the one or moresensor groups. Increasing the number of sensors may improve the accuracyof information describing the sound field produced by the transducerarray 410. Each sensor is configured to detect sound and convert thedetected sound into an electronic format.

The controller 430 (e.g. controller 365) controls the operation of theaudio system 400. In some embodiments, the controller 430 is configuredto mitigate crosstalk produced by the audio system 400. The controller430 includes a data store 440, a transfer function module 450, anoptimization module 460, and a sound filter module 470. The controller430 may be located inside the headset, in some embodiments. Someembodiments of the controller 430 have different components than thosedescribed here. Similarly, functions can be distributed among thecomponents in different manners than described here. For example, somefunctions of the controller may be performed external to the headset.

The data store 440 stores data for use by the audio system 400. Data inthe data store 440 may include sounds recorded in the local area of theheadset, audio content, preset audio content such as reference signals,head-related transfer functions (HRTFs), transfer functions for one ormore sensors and/or transducers, array transfer functions (ATFs) forsensors and/or transducers, optimization constraints, sound filters,model for a head of a user, and other data relevant for use by the audiosystem 400, or any combination thereof. The sounds recorded in the localarea of the headset may include data collected by the sensor array 420.The data store 440, in some embodiments, includes data on which soundsource regions (e.g., ears) the controller 430 designates as the brightzone and the quiet zone.

The transfer function module 450 estimates array transfer functions(ATFs) using data captured by a plurality of sensor groups in the sensorarray 420. A sensor group includes one or more sensors. Each sensorgroup is configured to monitor a specific sound source region. Forexample, in one embodiment, there is a sensor group that monitors theaudio content at a sound source region associated with the right ear anda second sensor group that monitors the audio content at a sound sourceregion associated with the left ear.

As discussed above, the ATFs comprise a number of transfer functionsthat characterize the relationship between the sound produced bytransducers in the transducer array 410 and the corresponding soundreceived by the sensors in the sensor array 420. A plurality of transferfunctions for a set of transducers or sensors are referred to as anarray transfer function. In some embodiments, Eigen-value decompositionis used to determine a transfer function. In some embodiments,singular-value decomposition is used to determine the transfer function.For a given transducer and/or sensor, a collection of transfer functionsfor all of the sensors in the sensor array is referred to as an ATF. AnATF characterizes how the sensor array 420 receives a sound from thetransducer and characterizes how the transducer array 410 producessound. An ATF also defines a relationship between parameters of thesound at the location of the transducer and the parameters at which thesensor array 420 detected the sound. In some embodiments, a RelativeTransfer Function (RTF) is another type of ATF that is normalized by anarbitrary sensor on the sensor array 420. An RTF may be normalized by anarbitrary transducer on the transducer array 410.

The optimization module 460 produces one or more sound filters to beapplied to transducers in the transducer array 410. The optimizationmodule 460 takes in the ATFs estimated by the transfer function module450 as input, and applies an optimization algorithm to the ATFs. Theoptimization algorithm may be subject to one or more constraints, storedin the data store 440, and outputs sound filters accordingly.Constraints may include, among others, designation of a left ear as abright zone or a quiet zone, designation of a right ear as a bright zoneor a quiet zone, a type of conduction (e.g., air, cartilage, and/orbone) by which the sound was transmitted to the user, or somecombination thereof. Some constraints may relate to the user of theheadset, such as head-related transfer functions, models of the user'shead, photos of the user, constraints that depend on demographicinformation, or some combination thereof. Other constraints may includea direction of propagation of the reproduced waves through the user'stissue and/or bone, the shape of the sound field produced through theuser's tissue and/or bone, or some combination thereof. The optimizationalgorithm may be linearly constrained, e.g., a linearly constrainedminimum variance (LCMV) algorithm, an imperialist competitive algorithm,or an algorithm that uses principal component analysis. The optimizationalgorithm may be an algorithm not mentioned herein. The sound filtersoutput by the optimization module 460 are input into the sound filtermodule 470. The sound filters may amplify or attenuate the acousticpressure waves presented by one or more of the transducers, may targetspecific frequency ranges differently, or some combination thereof.Sound filters may include, among others, low pass filters, high passfilters, and bandpass filters.

In some embodiments, the optimization module 460 applies theoptimization algorithm for a first ear being the bright zone, and thesecond ear as being the quiet zone, to generate a first set one or moresound filters. The optimization module 460 also applies the optimizationalgorithm for the second ear being the bright zone, and the first ear asbeing the quiet zone, to generate a second set of one or more soundfilters. The above processes may be done in parallel or in series.

The sound filter module 470 provides the sound filters to the transducerarray 410. The sound filters, as applied by transducer array 410, adjustthe audio content such that there is a dampened region (e.g., may be anull) at the ear designated as the quiet zone, while providing audiocontent to the other ear designated as the bright zone. By dampeningsound at regions that crosstalk may be perceived, the audio system 400described herein mitigates at least some of the crosstalk that resultsfrom tissue conduction.

FIG. 5 is a process 500 for mitigating crosstalk in a tissue conductionaudio system, according to one or more embodiments. The process shown inFIG. 5 may be performed by components of an audio system (e.g., audiosystem 400). Other entities may perform some or all of the steps in FIG.5 in other embodiments. Embodiments may include different and/oradditional steps, or perform the steps in different orders.

The audio system 400 designates 510 a first ear of a user wearing aheadset (e.g., headset 100) as a bright zone, and a second ear of theuser as a quiet zone.

The audio system 400 presents 520 audio content via a transducer array(e.g., transducer array 410) to the first ear of the user. The audiocontent may be, e.g., music, voice, etc. In some embodiments, the audiocontent may include a reference audio signal. The transducer arraypresents the audio content via tissue conduction to an inner ear of theear of the user. As the audio content is presented via tissueconduction, some of the audio content may also be received at the secondear of the user (i.e., crosstalk).

The audio system 400 monitors 530 data about the presented audio contentusing one or more sensors. The one or more sensors may be part of asensor array (e.g., the sensor array 420). The one or more sensorsinclude at least one sensor configured to capture data about thepresented audio content at the other ear of the user. The captured dataincludes data describing audio content intended for the first ear, butdetected at the second ear (i.e., crosstalk).

The audio system 400 estimates 540 array transfer functions (ATFs)associated with the presented audio content. The ATFs, estimated by acontroller (e.g., controller 430) are calculated using data captured bythe one or more sensors (e.g., via eigen value decomposition). ATFs arecalculated for each transducer in the transducer array 410.

The audio system 400 generates 550 sound filters for the transducerarray using the estimated ATFs. The audio system 400 may generate thesound filters using a controller (e.g., the controller 430) of the audiosystem 400.

The audio system 400 presents 560 adjusted audio content, via thetransducer array, based in part on the sound filters. The adjusted audiocontent has a damped region at the second ear such that the amplitude ofthe adjusted audio content at the first ear has a higher amplitude thanat the second ear. Accordingly, the adjusted audio content may filterout crosstalk, that would otherwise occur at the second ear.

Note that the above process is described for providing content to thefirst ear in a manner that mitigates crosstalk with the second ear. Theaudio system 400 may perform a similar process, but reverse which ear isin the bright zone and which ear is in the quiet zone to provide audiocontent to the second ear, while mitigating crosstalk with the firstear. Sound filters for each ear may be generated in parallel and/or inseries with one another, such that they are generated within a durationof the adjusted audio content. Each ear, however, receives audio contentin parallel.

Example of an Artificial Reality System

FIG. 6 is a block diagram of an example artificial reality system 600,according to one or more embodiments. The artificial reality system 600presents an artificial reality environment to a user, e.g., a virtualreality, an augmented reality, a mixed reality environment, or somecombination thereof. The system 600 comprises a headset 605 and aninput/output (I/O) interface, both of which are coupled to a console610. The headset 605 may be an embodiment of the headset 100. While FIG.6 shows an example system with one headset, one console, and one I/Ointerface, in other embodiments, any number of these components may beincluded in the system 600.

The headset 605 presents content to a user comprising augmented views ofa physical, real-world environment with computer-generated elements(e.g., two dimensional (2D) or three dimensional (3D) images, 2D or 3Dvideo, sound, etc.). The headset 605 may be an eyewear device or ahead-mounted display. In some embodiments, the presented contentincludes audio content that is presented via the audio system 400 thatreceives audio information (e.g., an audio signal) from the headset 605,the console 610, or both, and presents audio content based on the audioinformation. The headset 605 presents artificial reality content to theuser. The headset 605 includes the audio system 400, a depth cameraassembly (DCA) 630, an electronic display 635, an optics block 640, oneor more position sensors 645, and an inertial measurement unit (IMU)650. In some embodiments, the headset 605 includes components differentfrom those described here. Additionally, the functionality of variouscomponents may be distributed differently than what is described here.

The audio system 400 provides audio content to the user of the headset605. As described above, with reference to FIGS. 1-5, the audio system400 presents audio content via the transducer array 410, and capturesdata about the presented audio content via the sensor array 420. Theaudio system 400 determines sound filters that adjust audio content in amanner that mitigates crosstalk produced by tissue conduction.

The DCA 630 captures data describing depth information of a localenvironment surrounding some or all of the headset 605. The DCA 630 mayinclude a light generator (e.g., structured light and/or a flash fortime-of-flight), one or more imaging devices, a DCA controller, or somecombination thereof. The light generator illuminates a local area withillumination light, e.g., in accordance with emission instructionsgenerated by the DCA controller. The DCA controller is configured tocontrol, based on the emission instructions, operation of certaincomponents of the light generator, e.g., to adjust an intensity and apattern of the illumination light illuminating the local area. In someembodiments, the illumination light may include a structured lightpattern, e.g., dot pattern, line pattern, etc. In some embodiments, theillumination light may be used to provide additional texture for activestereo imaging via two or more imaging devices.

The one or more imaging device captures one or more images of one ormore objects in the local area. In some embodiments, there are aplurality of imaging devices and depth is determined stereo. In someembodiments, the one or more objects are illuminated with theillumination light. In these instances, the DCA controller may determinethe depth information using, e.g., structured light depth processingtechniques, ToF depth processing techniques, active stereo depthprocessing techniques, stereo depth processing techniques, or somecombination thereof. The DCA 630 may send the depth information toanother device such as the console 610. In some embodiments, the DCA 630may provide the captured images to the console 610, and the console 610determines the depth information.

The electronic display 635 displays 2D or 3D images to the user inaccordance with data received from the console 610. In variousembodiments, the electronic display 635 comprises a single electronicdisplay or multiple electronic displays (e.g., a display for each eye ofa user). Examples of the electronic display 635 include: a liquidcrystal display (LCD), an organic light emitting diode (OLED) display,an active-matrix organic light-emitting diode display (AMOLED),waveguide display, some other display, or some combination thereof.

In some embodiments, the optics block 640 magnifies image light receivedfrom the electronic display 635, corrects optical errors associated withthe image light, and presents the corrected image light to a user of theheadset 605. In various embodiments, the optics block 640 includes oneor more optical elements. Example optical elements included in theoptics block 640 include: a waveguide, an aperture, a Fresnel lens, aconvex lens, a concave lens, a filter, a reflecting surface, or anyother suitable optical element that affects image light. Moreover, theoptics block 640 may include combinations of different optical elements.In some embodiments, one or more of the optical elements in the opticsblock 640 may have one or more coatings, such as partially reflective oranti-reflective coatings.

Magnification and focusing of the image light by the optics block 640allows the electronic display 635 to be physically smaller, weigh less,and consume less power than larger displays. Additionally, magnificationmay increase the field of view of the content presented by theelectronic display 635. For example, the field of view of the displayedcontent is such that the displayed content is presented using almost all(e.g., approximately 110 degrees diagonal), and in some cases, all ofthe user's field of view. Additionally, in some embodiments, the amountof magnification may be adjusted by adding or removing optical elements.

In some embodiments, the optics block 640 may be designed to correct oneor more types of optical error. Examples of optical error include barrelor pincushion distortion, longitudinal chromatic aberrations, ortransverse chromatic aberrations. Other types of optical errors mayfurther include spherical aberrations, chromatic aberrations, or errorsdue to the lens field curvature, astigmatisms, or any other type ofoptical error. In some embodiments, content provided to the electronicdisplay 635 for display is predistorted, and the optics block 640corrects the distortion when it receives image light from the electronicdisplay 635 generated based on the content.

The IMU 650 is an electronic device that generates data indicating aposition of the headset 605 based on measurement signals received fromone or more of the position sensors 645. A position sensor 645 generatesone or more measurement signals in response to motion of the headset605. Examples of position sensors 645 include: one or moreaccelerometers, one or more gyroscopes, one or more magnetometers,another suitable type of sensor that detects motion, a type of sensorused for error correction of the IMU 650, or some combination thereof.The position sensors 645 may be located external to the IMU 650,internal to the IMU 650, or some combination thereof. In one or moreembodiments, the IMU 650 and/or the position sensor 645 may be sensorsin the sensor array 420, configured to capture data about the audiocontent presented by audio content 400.

Based on the one or more measurement signals from one or more positionsensors 645, the IMU 650 generates data indicating an estimated currentposition of the headset 605 relative to an initial position of theheadset 605. For example, the position sensors 645 include multipleaccelerometers to measure translational motion (forward/back, up/down,left/right) and multiple gyroscopes to measure rotational motion (e.g.,pitch, yaw, and roll). In some embodiments, the IMU 650 rapidly samplesthe measurement signals and calculates the estimated current position ofthe headset 605 from the sampled data. For example, the IMU 650integrates the measurement signals received from the accelerometers overtime to estimate a velocity vector and integrates the velocity vectorover time to determine an estimated current position of a referencepoint on the headset 605. Alternatively, the IMU 650 provides thesampled measurement signals to the console 610, which interprets thedata to reduce error. The reference point is a point that may be used todescribe the position of the headset 605. The reference point maygenerally be defined as a point in space or a position related to theeyewear device's 605 orientation and position.

The I/O interface 655 is a device that allows a user to send actionrequests and receive responses from the console 610. An action requestis a request to perform a particular action. For example, an actionrequest may be an instruction to start or end capture of image or videodata, or an instruction to perform a particular action within anapplication. The I/O interface 655 may include one or more inputdevices. Example input devices include: a keyboard, a mouse, a handcontroller, or any other suitable device for receiving action requestsand communicating the action requests to the console 610. An actionrequest received by the I/O interface 655 is communicated to the console610, which performs an action corresponding to the action request. Insome embodiments, the I/O interface 515 includes an IMU 650, as furtherdescribed above, that captures calibration data indicating an estimatedposition of the I/O interface 655 relative to an initial position of theI/O interface 655. In some embodiments, the I/O interface 655 mayprovide haptic feedback to the user in accordance with instructionsreceived from the console 610. For example, haptic feedback is providedwhen an action request is received, or the console 610 communicatesinstructions to the I/O interface 655 causing the I/O interface 655 togenerate haptic feedback when the console 610 performs an action. TheI/O interface 655 may monitor one or more input responses from the userfor use in determining a perceived origin direction and/or perceivedorigin location of audio content.

The console 610 provides content to the headset 605 for processing inaccordance with information received from one or more of: the headset605 and the I/O interface 655. In the example shown in FIG. 6, theconsole 610 includes an application store 620, a tracking module 625 andan engine 615. Some embodiments of the console 610 have differentmodules or components than those described in conjunction with FIG. 6.Similarly, the functions further described below may be distributedamong components of the console 610 in a different manner than describedin conjunction with FIG. 6.

The application store 620 stores one or more applications for executionby the console 610. An application is a group of instructions, that whenexecuted by a processor, generates content for presentation to the user.Content generated by an application may be in response to inputsreceived from the user via movement of the headset 605 or the I/Ointerface 655. Examples of applications include: gaming applications,conferencing applications, video playback applications, or othersuitable applications.

The tracking module 625 calibrates the system environment 600 using oneor more calibration parameters and may adjust one or more calibrationparameters to reduce error in determination of the position of theheadset 605 or of the I/O interface 655. Calibration performed by thetracking module 625 also accounts for information received from the IMU650 in the headset 605 and/or an IMU 650 included in the I/O interface655. Additionally, if tracking of the headset 605 is lost, the trackingmodule 625 may re-calibrate some or all of the system environment 600.

The tracking module 625 tracks movements of the headset 605 or of theI/O interface 655 using information from the one or more positionsensors 645, the IMU 650, the DCA 630, or some combination thereof. Forexample, the tracking module 625 determines a position of a referencepoint of the headset 605 in a mapping of a local area based oninformation from the headset 605. The tracking module 625 may alsodetermine positions of the reference point of the headset 605 or areference point of the I/O interface 655 using data indicating aposition of the headset 605 from the IMU 650 or using data indicating aposition of the I/O interface 655 from an IMU 650 included in the I/Ointerface 655, respectively. Additionally, in some embodiments, thetracking module 625 may use portions of data indicating a position orthe headset 605 from the IMU 650 to predict a future position of theheadset 605. The tracking module 625 provides the estimated or predictedfuture position of the headset 605 or the I/O interface 655 to theengine 615. In some embodiments, the tracking module 625 may providetracking information to the audio system 400 for use in generating thesound filters. The engine 615 also executes applications within thesystem environment 600 and receives position information, accelerationinformation, velocity information, predicted future positions, or somecombination thereof, of the headset 605 from the tracking module 625.Based on the received information, the engine 615 determines content toprovide to the headset 605 for presentation to the user. For example, ifthe received information indicates that the user has looked to the left,the engine 615 generates content for the headset 605 that mirrors theuser's movement in a virtual environment or in an environment augmentingthe local area with additional content. Additionally, the engine 615performs an action within an application executing on the console 610 inresponse to an action request received from the I/O interface 655 andprovides feedback to the user that the action was performed. Theprovided feedback may be visual or audible feedback via the headset 605or haptic feedback via the I/O interface 655.

Additional Configuration Information

The foregoing description of the embodiments of the disclosure has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Some portions of this description describe the embodiments of thedisclosure in terms of algorithms and symbolic representations ofoperations on information. These algorithmic descriptions andrepresentations are commonly used by those skilled in the dataprocessing arts to convey the substance of their work effectively toothers skilled in the art. These operations, while describedfunctionally, computationally, or logically, are understood to beimplemented by computer programs or equivalent electrical circuits,microcode, or the like, in relation to manufacturing processes.Furthermore, it has also proven convenient at times, to refer to thesearrangements of operations as modules, without loss of generality. Thedescribed operations and their associated modules may be embodied insoftware, firmware, hardware, or any combinations thereof.

Any of the steps, operations, or processes described herein may beperformed or implemented with one or more hardware or software modules,alone or in combination with other devices. In one embodiment, asoftware module is implemented with a computer program productcomprising a computer-readable medium containing computer program code,which can be executed by a computer processor for performing any or allof the steps, operations, or processes described (e.g., in relation tomanufacturing processes.

Embodiments of the disclosure may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, and/or it may comprise ageneral-purpose computing device selectively activated or reconfiguredby a computer program stored in the computer. Such a computer programmay be stored in a non-transitory, tangible computer readable storagemedium, or any type of media suitable for storing electronicinstructions, which may be coupled to a computer system bus.Furthermore, any computing systems referred to in the specification mayinclude a single processor or may be architectures employing multipleprocessor designs for increased computing capability.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the inventive subject matter.It is therefore intended that the scope of the disclosure be limited notby this detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

What is claimed is:
 1. A method comprising: presenting audio content viaa transducer array that presents audio content via tissue conduction toan inner ear of a first ear of a user; monitoring, via one or moresensors on a headset, data about the presented audio content, the one ormore sensors including a first group of sensors and a second group ofsensors, and the first group of sensors is proximate to the first ear,and the second group of sensors is proximate to a second ear of the userand includes the at least one sensor, and at least one sensor of the oneor more sensors is configured to capture data about the presented audiocontent at the second ear; estimating array transfer functions (ATFs)associated with the data; generating sound filters for the transducerarray using the estimated ATFs; and presenting adjusted audio content,via the transducer array, based in part on the sound filters, whereinthe adjusted audio content has a damped region at the second ear suchthat the amplitude of the adjusted audio content at the first ear has ahigher amplitude than at the second ear.
 2. The method of claim 1,wherein the tissue conduction includes at least one of cartilageconduction and bone conduction.
 3. The method of claim 1, wherein thetransducer array includes a first group of transducers and a secondgroup of transducers, and the first group of transducers is proximate tothe first ear, and the second group of transducers is proximate to thesecond ear.
 4. The method of claim 1, wherein monitoring, via the one ormore sensors on the headset, data about the presented audio content,includes: monitoring data about the presented audio content using atleast one of the first group of sensors and the second group of sensors.5. The method of claim 1, further comprising: presenting second audiocontent via the transducer array that presents the second audio contentvia tissue conduction to an inner ear of a second ear; monitoring, viaat least one sensor on the headset, second data about the presentedsecond audio content, the at least one sensor including at least onesensor configured to capture second data about the presented secondaudio content at the second ear; estimating second array transferfunctions (ATFs) associated with the second data; generating secondsound filters for the transducer array using the estimated second ATFs;and presenting adjusted second audio content, via the transducer array,based in part on the second sound filters, wherein the adjusted audiocontent has a damped region at the first ear such that the amplitude ofthe adjusted audio content at the first ear has a higher amplitude thanat the second ear.
 6. The method of claim 5, wherein presenting adjustedaudio content and presenting adjusted second audio content occurs overdifferent time periods.
 7. An audio system comprising: a transducerarray configured to present audio content via tissue conduction to aninner ear of a first ear of a user; one or more sensors on a headsetconfigured to monitor data about the presented audio content, the one ormore sensors including a first group of sensors and a second group ofsensors, and the first group of sensors is proximate to the first ear,and the second group of sensors is proximate to a second ear of the userand includes the at least one sensor, and at least one sensor of the oneor more sensors is configured to capture data about the presented audiocontent at the second ear; a controller configured to: estimate arraytransfer functions (ATFs) associated with the data, generate soundfilters for the transducer array using the estimated ATFs, and instructthe transducer array to present adjusted audio content, based in part onthe sound filters, wherein the adjusted audio content has a dampedregion at the second ear such that the amplitude of the audio content atthe first ear has a higher amplitude than at the second ear.
 8. Theaudio system of claim 7, wherein the tissue conduction includes at leastone of cartilage conduction and bone conduction.
 9. The audio system ofclaim 8, wherein the transducer array includes a first group oftransducers and a second group of transducers, and the first group oftransducers is proximate to the first ear, and the second group oftransducers is proximate to the second ear.
 10. The audio system ofclaim 7, wherein the transducer array is configured to present secondaudio content via tissue conduction to an inner ear of a second ear ofthe user, and the audio system further comprises one or more sensors ona headset configured to monitor second data about the presented audiocontent, the one or more sensors including at least one sensorconfigured to capture second data about the presented audio content atthe second ear; wherein the controller is further configured to:estimate second array transfer functions (ATFs) associated with thesecond data, generate second sound filters for the transducer arrayusing the estimated second ATFs, and instruct the transducer array topresent adjusted second audio content, based in part on the second soundfilters, wherein the adjusted audio content has a damped region at thefirst ear such that the amplitude of the adjusted audio content at thesecond ear has a higher amplitude than at the first ear.
 11. The audiosystem of claim 10, wherein presenting adjusted audio content andpresenting adjusted second audio content occurs over different timeperiods.
 12. A non-transitory computer readable medium configured tostore program code instructions, when executed by a processor, cause theprocessor to perform steps comprising: presenting audio content via atransducer array that presents audio content via tissue conduction to aninner ear of a first ear of a user; monitoring, via one or more sensorson a headset, data about the presented audio content, the one or moresensors including a first group of sensors and a second group ofsensors, and the first group of sensors is proximate to the first ear,and the second group of sensors is proximate to a second ear of the userand include the at least one sensor, and at least one sensor of the oneor more sensors is configured to capture data about the presented audiocontent at the second ear; estimating array transfer functions (ATFs)associated with the data; generating sound filters for the transducerarray using the estimated ATFs; and presenting adjusted audio content,via the transducer array, based in part on the sound filters, whereinthe adjusted audio content has a damped region at the second ear suchthat the amplitude of the adjusted audio content at the first ear has ahigher amplitude than at the second ear.
 13. The non-transitory computerreadable medium of claim 12, the steps further comprising: presentingsecond audio content via the transducer array that presents the secondaudio content via tissue conduction to an inner ear of a second ear;monitoring, via at least one sensor on the headset, second data aboutthe presented second audio content, the at least one sensor including atleast one sensor configured to capture second data about the presentedsecond audio content at the second ear; estimating second array transferfunctions (ATFs) associated with the second data; generating secondsound filters for the transducer array using the estimated second ATFs;and presenting adjusted second audio content, via the transducer array,based in part on the second sound filters, wherein the adjusted audiocontent has a damped region at the first ear such that the amplitude ofthe adjusted audio content at the first ear has a higher amplitude thanat the second ear.
 14. The non-transitory computer readable medium ofclaim 12, wherein the tissue conduction includes at least one ofcartilage conduction and bone conduction.
 15. A method comprising:presenting audio content via a transducer array that presents audiocontent via tissue conduction to an inner ear of a first ear of a user;monitoring, via one or more sensors on a headset, data about thepresented audio content, the one or more sensors including at least onesensor configured to capture data about the presented audio content at asecond ear of the user; estimating array transfer functions (ATFs)associated with the data; generating sound filters for the transducerarray using the estimated ATFs, wherein generating the sound filterscomprises: applying an optimization algorithm to the estimated ATFs togenerate the sound filters, the optimization algorithm subject to one ormore constraints, and the one or more constraints include that the firstear is designated as a bright zone, and that the second ear isdesignated as a quiet zone; and presenting adjusted audio content, viathe transducer array, based in part on the sound filters, wherein theadjusted audio content has a damped region at the second ear such thatthe amplitude of the adjusted audio content at the first ear has ahigher amplitude than at the second ear.
 16. An audio system comprising:a transducer array configured to present audio content via tissueconduction to an inner ear of a first ear of a user; one or more sensorson a headset configured to monitor data about the presented audiocontent, the one or more sensors including at least one sensorconfigured to capture data about the presented audio content at a secondear; a controller configured to: estimate array transfer functions(ATFs) associated with the data, apply an optimization algorithm to theestimated ATFs to generate sound filters for the transducer array, theoptimization algorithm subject to one or more constraints, and the oneor more constraints include that the first ear is designated as a brightzone, and that the second ear is designated as a quiet zone; andinstruct the transducer array to present adjusted audio content, basedin part on the sound filters, wherein the adjusted audio content has adamped region at the second ear such that the amplitude of the audiocontent at the first ear has a higher amplitude than at the second ear.17. A non-transitory computer readable medium configured to storeprogram code instructions, when executed by a processor, cause theprocessor to perform steps comprising: presenting audio content via atransducer array that presents audio content via tissue conduction to aninner ear of a first ear of a user; monitoring, via one or more sensorson a headset, data about the presented audio content, the one or moresensors including at least one sensor configured to capture data aboutthe presented audio content at a second ear of the user; estimatingarray transfer functions (ATFs) associated with the data; generatingsound filters for the transducer array using the estimated ATFs, whereingenerating the sound filters comprises: applying an optimizationalgorithm to the estimated ATFs to generate the sound filters, theoptimization algorithm subject to one or more constraints, and the oneor more constraints include that the first ear is designated as a brightzone, and that the second ear is designated as a quiet zone; andpresenting adjusted audio content, via the transducer array, based inpart on the sound filters, wherein the adjusted audio content has adamped region at the second ear such that the amplitude of the adjustedaudio content at the first ear has a higher amplitude than at the secondear.